Showerhead assembly with metrology port purge

ABSTRACT

A method and apparatus that may be utilized for chemical vapor deposition and/or hydride vapor phase epitaxial (HVPE) deposition are provided. In one embodiment, the apparatus is a processing chamber that includes a showerhead with separate inlets and channels for delivering separate processing gases into a processing volume of the chamber without mixing the gases prior to entering the processing volume. In one embodiment, the showerhead includes metrology ports with purge gas assemblies configured and positioned to deliver a purge gas to prevent deposition thereon. In one embodiment, the metrology port is configured to receive a temperature measurement device, and the purge gas assembly is a concentric tube configuration configured to prevent deposition on components of the temperature measurement device. In one embodiment, the metrology port has a sensor window and is configured to receive an optical measurement device, and the purge gas assembly and sensor window are configured to prevent deposition on the sensor window.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/324,271 (APPM/015324L), filed Apr. 14, 2010, which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to methods and apparatus for chemical vapor deposition (CVD) on a substrate, and, in particular, to a showerhead design for use in metal organic chemical vapor deposition (MOCVD) and/or hydride vapor phase epitaxy (HVPE).

2. Description of the Related Art

Group III-V films are finding greater importance in the development and fabrication of a variety of semiconductor devices, such as short wavelength light emitting diodes (LEDs), laser diodes (LDs), and electronic devices including high power, high frequency, high temperature transistors and integrated circuits. For example, short wavelength (e.g., blue/green to ultraviolet) LEDs are fabricated using the Group III-nitride semiconducting material gallium nitride (GaN). It has been observed that short wavelength LEDs fabricated using GaN can provide significantly greater efficiencies and longer operating lifetimes than short wavelength LEDs fabricated using non-nitride semiconducting materials, such as Group II-VI materials.

One method that has been used for depositing Group III-nitrides, such as GaN, is metal organic chemical vapor deposition (MOCVD). This chemical vapor deposition method is generally performed in a reactor having a temperature controlled environment to assure the stability of a first precursor gas which contains at least one element from Group III, such as gallium (Ga). A second precursor gas, such as ammonia (NH₃), provides the nitrogen needed to form a Group III-nitride. The two precursor gases are injected into a processing zone within the reactor where they mix and move towards a heated substrate in the processing zone. A carrier gas may be used to assist in the transport of the precursor gases towards the substrate. The precursors react at the surface of the heated substrate to form a Group III-nitride layer, such as GaN, on the substrate surface. The quality of the film depends in part upon deposition uniformity which, in turn, depends upon uniform mixing of the precursors across the substrate.

Multiple substrates may be arranged on a substrate carrier and each substrate may have a diameter ranging from 50 mm to 100 mm or larger. The uniform mixing of precursors over larger substrates and/or more substrates and larger deposition areas is desirable in order to increase yield and throughput. These factors are important since they directly affect the cost to produce an electronic device and, thus, a device manufacturer's competitiveness in the marketplace.

Interaction of the precursor gases with the hot hardware components, which are often found in the processing zone of an LED or LD forming reactor, generally causes the precursor to break-down and deposit on these hot surfaces. Typically, the hot reactor surfaces are formed by radiation from the heat sources used to heat the substrates. The deposition of the precursor materials on the hot surfaces can be especially problematic when it occurs in or on the precursor distribution components, such as the showerhead. Deposition on the precursor distribution components affects the flow distribution uniformity over time. Additionally, deposition on metrology ports disposed in the precursor distribution components affects the accurate measurement and control of conditions within the processing zone of the reactor. Therefore, there is a need for a gas distribution apparatus that prevents or reduces the likelihood that the MOCVD precursors, or HVPE precursors, are heated to a temperature that causes them to break down and affect the performance of the gas distribution and metrology components.

Also, as the demand for LEDs, LDs, transistors, and integrated circuits increases, the efficiency of depositing high quality Group-III nitride films takes on greater importance. Therefore, there is a need for an improved deposition apparatus and process that can provide consistent film quality over larger substrates and larger deposition areas.

SUMMARY OF THE INVENTION

The present invention generally provides improved methods and apparatus for depositing Group III-nitride films using MOCVD and/or HVPE processes.

One embodiment of the present invention provides a showerhead assembly comprising a showerhead having a first metrology port defining an interior region and extending through the showerhead and a second metrology port extending through the showerhead. The showerhead assembly further comprises a first metrology assembly having an optical element that is at least partially disposed within the interior region of the first metrology port, a first purge gas assembly having a first gas inlet coupled to a purge gas source and configured to direct a purge gas through the interior region of the first metrology port to prevent deposition of material on the optical element, a second metrology assembly having a sensor window disposed adjacent the second metrology port, and a second purge gas assembly having a gas inlet coupled to the purge gas source and configured to direct the purge gas toward the sensor window to prevent deposition of material thereon.

Another embodiment provides a showerhead assembly comprising a showerhead having a metrology port defining an interior region and extending through the showerhead, a metrology assembly having an optical element that is at least partially disposed within the interior region of the metrology port, and a purge gas assembly having a first gas inlet coupled to a purge gas source and configured to direct a purge gas toward the optical element to prevent deposition of material thereon, wherein a sheath is concentrically disposed about the optical element and within the interior region, and wherein the sheath has an aperture in fluid communication with the first gas inlet.

Yet another embodiment of the present invention provides a showerhead assembly comprising a showerhead having a metrology port extending through the showerhead, a metrology assembly having a sensor window disposed adjacent the metrology port, and a purge gas assembly having a gas inlet coupled to a purge gas source and a gas distribution device having an annular channel in fluid communication with the gas inlet, wherein the gas distribution device is configured to direct the purge gas into a vortex adjacent the sensor window.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 is a schematic plan view illustrating one embodiment of a processing system for fabricating compound nitride semiconductor devices according to embodiments described herein.

FIG. 2 is a schematic cross-sectional view of a metal-organic chemical vapor deposition (MOCVD) chamber for fabricating compound nitride semiconductor devices according to one embodiment of the present invention.

FIG. 3 is a schematic, cross-sectional view of a first metrology assembly attached to the showerhead depicted in FIG. 2 according to one embodiment of the present invention.

FIG. 4A is a schematic, cross-sectional view of a second metrology assembly attached to the showerhead depicted in FIG. 2 according to one embodiment of the present invention.

FIG. 4B is a top view of a gas distribution device depicted in FIG. 4A according to one embodiment.

FIG. 5A is a schematic, cross-sectional view of the second metrology assembly attached to the showerhead depicted in FIG. 2 according to another embodiment of the present invention.

FIG. 5B is a schematic, cross-sectional view of a sensor window as it is positioned in the second metrology assembly in FIG. 5A according to one embodiment.

FIG. 5C is a schematic, cross-sectional view of the sensor window as it is positioned in the second metrology assembly in FIG. 5A according to another embodiment.

FIG. 6A is a schematic bottom view of the showerhead in FIG. 2 according to one embodiment.

FIG. 6B is a schematic bottom view of the showerhead in FIG. 2 according to another embodiment.

FIG. 6C is an enlarged view of a portion of the surface of the showerhead shown in FIG. 6A.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

Embodiments of the present invention generally provide a method and apparatus that may be utilized for deposition of Group III-nitride films using MOCVD and/or HVPE hardware. In one embodiment, the apparatus is a processing chamber that includes a showerhead with separate inlets and channels for delivering separate processing gases into a processing volume of the chamber without mixing the gases prior to entering the processing volume. In one embodiment, the showerhead includes metrology ports with purge gas assemblies configured and positioned to deliver a purge gas to prevent deposition thereon. In one embodiment, the metrology port is configured to receive a temperature measurement device, and the purge gas assembly is a concentric tube configuration configured to prevent deposition on components of the temperature measurement device. In one embodiment, the metrology port has a sensor window and is configured to receive an optical measurement device that is configured to deliver and receive electromagnetic energy through the sensor window to measure a property of one or more substrates disposed in a processing region of the processing chamber. In certain embodiments of the invention, the purge gas assembly and sensor window are configured to prevent the obstruction of the delivery or reception of the electromagnetic energy, due to the deposition of material on the sensor window.

FIG. 1 is a schematic plan view illustrating one embodiment of a processing system 100 that comprises the one or more MOCVD chambers 102 for fabricating compound nitride semiconductor devices according to embodiments described herein. In one embodiment, the processing system 100 is closed to atmosphere. The processing system 100 comprises a transfer chamber 106, a MOCVD chamber 102 coupled with the transfer chamber 106, a loadlock chamber 108 coupled with the transfer chamber 106, a batch loadlock chamber 109, for storing substrates, coupled with the transfer chamber 106, and a load station 110, for loading substrates, coupled with the loadlock chamber 108. The transfer chamber 106 comprises a robot assembly (not shown) operable to pick up and transfer substrates between the loadlock chamber 108, the batch loadlock chamber 109, and the MOCVD chamber 102. Although a single MOCVD chamber 102 is shown, it should be understood that more than one MOCVD chamber 102 or additionally, combinations of one or more MOCVD chambers 102 with one or more Hydride Vapor Phase Epitaxial (HVPE) chambers may also be coupled with the transfer chamber 106. It should also be understood that although a cluster tool is shown, the embodiments described herein may be performed using linear track systems.

In one embodiment, the transfer chamber 106 remains under vacuum during substrate transfer processes. The transfer chamber vacuum level may be adjusted to match the vacuum level of the MOCVD chamber 102. For example, when transferring substrates from a transfer chamber 106 into the MOCVD chamber 102 (or vice versa), the transfer chamber 106 and the MOCVD chamber 102 may be maintained at the same vacuum level. Then, when transferring substrates from the transfer chamber 106 to the load lock chamber 108 (or vice versa) or the batch load lock chamber 109 (or vice versa), the transfer chamber vacuum level may be adjusted to match the vacuum level of the loadlock chamber 108 or batch load lock chamber 109 even through the vacuum level of the loadlock chamber 108 or batch load lock chamber 109 and the MOCVD chamber 102 may be different. Thus, the vacuum level of the transfer chamber 106 is adjustable. In certain embodiments, substrates are transferred in a high purity inert gas environment, such as, a high purity N₂ environment. In one embodiment, substrates transferred in an environment having greater than 90% N₂. In certain embodiments, substrates are transferred in a high purity NH₃ environment. In one embodiment, substrates are transferred in an environment having greater than 90% NH₃. In certain embodiments, substrates are transferred in a high purity H₂ environment. In one embodiment, substrates are transferred in an environment having greater than 90% H₂.

In the processing system 100, the robot assembly (not shown) transfers a substrate carrier plate 112 loaded with substrates into the single MOCVD chamber 102 to undergo deposition. In one embodiment, the substrate carrier plate 112 may have a diameter ranging from about 200 mm to about 750 mm. The substrate carrier plate 112 may be formed from a variety of materials, including SiC or SiC-coated graphite. In one embodiment, the substrate carrier plate 112 comprises a silicon carbide material. In one embodiment, the substrate carrier plate 112 has a surface area of about 1,000 cm² or more, preferably 2,000 cm² or more, and more preferably 4,000 cm² or more. After some or all deposition steps have been completed, the substrate carrier plate 112 is transferred from the MOCVD chamber 102 back to the loadlock chamber 108 via the transfer robot. In one embodiment, the substrate carrier plate 112 is then transferred to the load station 110. In another embodiment, the substrate carrier plate 112 may be stored in either the loadlock chamber 108 or the batch load lock chamber 109 prior to further processing in the MOCVD chamber 102. One exemplary processing system 100 that may be adapted in accordance with embodiments of the present invention is described in U.S. patent application Ser. No. 12/023,572, filed Jan. 31, 2008, now published as US 2009-0194026, entitled PROCESSING SYSTEM FOR FABRICATING COMPOUND NITRIDE SEMICONDUCTOR DEVICES, which is hereby incorporated by reference in its entirety.

In one embodiment, a system controller 160 controls activities and operating parameters of the processing system 100. The system controller 160 includes a computer processor and a computer-readable memory coupled to the processor. The processor executes system control software, such as a computer program stored in memory. Exemplary aspects of the processing system 100 and methods of use adaptable to embodiments of the present invention are further described in U.S. patent application Ser. No. 11/404,516, filed Apr. 14, 2006, now published as US 2007-024516, entitled EPITAXIAL GROWTH OF COMPOUND NITRIDE STRUCTURES, which is hereby incorporated by reference in its entirety.

FIG. 2 is a schematic cross-sectional view of the MOCVD chamber 102 according to embodiments of the present invention. The MOCVD chamber 102 comprises a chamber body 202, a chemical delivery module 203 for delivering precursor gases, carrier gases, cleaning gases, and/or purge gases, a remote plasma system 226 with a plasma source, a susceptor or substrate support 214, and a vacuum system 212. The chamber body 202 encloses a processing volume 208. A showerhead assembly 201 is disposed at one end of the processing volume 208, and the substrate carrier plate 112 is disposed at the other end of the processing volume 208. The substrate carrier plate 112 may be disposed on the substrate support 214. The substrate support 214 has z-lift capability for moving in a vertical direction, as shown by arrow 215. In one embodiment, the z-lift capability may be used to move the substrate support 214 upwardly, and closer to the showerhead assembly 201, and downwardly, and further away from the showerhead assembly 201. In one embodiment, the distance from the surface of the showerhead assembly 201 that is adjacent the processing volume 208 to the substrate carrier plate 112 during processing ranges from about 4 mm to about 41 mm. In certain embodiments, the substrate support 214 comprises a heating element (e.g., a resistive heating element (not shown)) for controlling the temperature of the substrate support 214 and consequently controlling the temperature of the substrate carrier plate 112 and substrates 240 positioned on the substrate carrier plate 112 and the substrate support 214.

In one embodiment, the showerhead assembly 201 includes a showerhead 204. In one embodiment, the showerhead 204 is a single plate having a plurality of channels and apertures formed therein. In another embodiment, the showerhead 204 includes a plurality of plates machined and attached such that a plurality of channels and apertures are formed therein. In one embodiment, the showerhead 204 has a first processing gas channel 204A coupled with the chemical delivery module 203 via a first processing gas inlet 259 for delivering a first precursor or first process gas mixture to the processing volume 208. In one embodiment, the chemical delivery module 203 is configured to deliver a metal organic precursor to the first processing gas channel 204A. In one example, the metal organic precursor comprises a suitable gallium (Ga) precursor (e.g., trimethyl gallium (“TMG”), triethyl gallium (TEG)), a suitable aluminum precursor (e.g., trimethyl aluminum (“TMA”)), or a suitable indium precursor (e.g., trimethyl indium (“TMI”)).

In one embodiment, a blocker plate 255 is positioned across the first processing gas channel 204A. The blocker plate 255 has a plurality of orifices 257 disposed therethrough. In one embodiment, the blocker plate 255 is positioned between the first processing gas inlet 259 and the first processing gas channel 204A for uniformly distributing gas received from the chemical delivery module 203 into the first processing gas channel 204A.

In one embodiment, the showerhead 204 has a second processing gas channel 204B coupled with the chemical delivery module 203 for delivering a second precursor or second process gas mixture to the processing volume 208 via a second processing gas inlet 258. In one embodiment, the chemical delivery module 203 is configured to deliver a suitable nitrogen containing processing gas, such as ammonia (NH₃) or other MOCVD or HVPE processing gas, to the second processing gas channel 204B. In one embodiment, the second processing gas channel 204B is separated from the first processing gas channel 204A by a first horizontal wall 276 of the showerhead 204.

The showerhead 204 may further include a temperature control channel 204C coupled with a heat exchanging system 270 for flowing a heat exchanging fluid through the showerhead 204 to help regulate the temperature of the showerhead 204. Suitable heat exchanging fluids include, but are not limited to, water, water-based ethylene glycol mixtures, a perfluoropolyether (e.g., Galden® fluid), oil-based thermal transfer fluids, or similar fluids. In one embodiment, the second processing gas channel 204B is separated from the temperature control channel 204C by a second horizontal wall 277 of the showerhead 204. The temperature control channel 204C may be separated from the processing volume 208 by a third horizontal wall 278 of the showerhead 204.

In one embodiment, the first precursor or first processing gas mixture, such as a metal organic precursor, is delivered from the first processing gas channel 204A through the second processing gas channel 204B and the temperature control channel 204C into the processing volume 208 via a plurality of inner gas conduits 246. The inner gas conduits 246 may be cylindrical tubes located within aligned holes disposed through the first horizontal wall 276, the second horizontal wall 277, and the third horizontal wall 278 of the showerhead 204. In one embodiment, the inner gas conduits 246 are each attached to the first horizontal wall 276 of the showerhead 204 by suitable means, such as brazing.

In one embodiment, the second precursor or second processing gas mixture, such as a nitrogen precursor, is delivered from the second processing gas channel 204B through the temperature control channel 204C and into the processing volume 208 via a plurality of outer gas conduits 245. The outer gas conduits 245 may be cylindrical tubes each located concentrically about a respective inner gas conduit 246. The outer gas conduits 245 are located within the aligned holes disposed through the second horizontal wall 277 and the third horizontal wall 278 of the showerhead 204. In one embodiment, the outer gas conduits 245 are each attached to the second horizontal wall 277 of the showerhead 204 by suitable means, such as brazing.

In certain embodiments of the present invention, a purge gas (e.g., nitrogen, hydrogen, argon) is delivered into the chamber 102 from the showerhead 204 through one or more purge gas channels 281 coupled to a purge gas source 282. In this embodiment, the purge gas is distributed through a plurality of orifices 284 about the periphery of the showerhead 204. The plurality of orifices 284 may be configured in a circular pattern about the periphery of the showerhead 204 and positioned distribute the purge gas about the periphery of the substrate carrier plate 112 to prevent undesirable deposition on edges of the substrate carrier plate 112, the showerhead 204, and other components of the chamber 102, which result in particle formation and, ultimately contamination of the substrates 240. The purge gas flows downwardly into multiple exhaust ports 209, which are disposed around an annular exhaust channel 205. An exhaust conduit 206 connects the annular exhaust channel 205 to a vacuum system 212, which includes a vacuum pump 207. The pressure of the chamber 102 may be controlled using a valve system, which controls the rate at which the exhaust gases are drawn from the annular exhaust channel 205.

In other embodiments, purge gas tubes 283 are disposed near the bottom of the chamber 102. In this configuration, the purge gas enters the lower volume 210 of the chamber 102 and flows upwardly past the substrate carrier plate 112 and exhaust ring 220 and into the multiple exhaust ports 209.

In one embodiment, the showerhead assembly 201 comprises a first metrology assembly 291 attached to a first metrology port 296 and a second metrology assembly 292 attached to a second metrology port 297. The first and second metrology ports 296, 297, each include a tube 298 that is positioned in an aperture formed through the showerhead 204 and attached to the showerhead 204, such as by brazing, such that each of the channels (204A, 204B, and 204C) are separated and sealed from one another. The first and second metrology assemblies 291, 292 are used to monitor the processes performed on the surface of the substrates 240 disposed in the processing volume 208 of the chamber 102. In one embodiment, the first metrology assembly 291 includes a temperature measurement device, such as an optical pyrometer.

In one embodiment, the second metrology assembly 292 includes an optical measurement device, such as an optical stress, or substrate bow, measurement device. Generally, the optical measurement device (not shown) includes an optical emitter, such as a light source, for emitting one or more beams of light through a sensor window disposed in the second metrology port 297 as subsequently described with respect to FIGS. 4 and 5. The beams of light are generally focused through the sensor window onto a substrate 240 disposed in the processing volume 208 of the chamber 102. The beams of light strike the substrate 240 and are reflected back through the sensor window and received by an optical detector within the optical measurement device. The received beams of light are then compared with the emitted beams of light to determine a property of the substrate 240, such as the amount of bow of the substrate 240 (i.e., amount of convex or concave curvature of the upper surface of the substrate 240).

In one embodiment, the first metrology assembly 291 and the second metrology assembly 292 include a first purge gas assembly 291A and a second purge gas assembly 292A, respectively, that are adapted to deliver and position a purge gas from the purge gas source 282 to the metrology assemblies 291, 292 so as to prevent deposition of material on the surface of components within the assemblies. In one embodiment, the first purge gas assembly 291A and second purge gas assembly 292A are further connected to a cleaning gas source (e.g., the chemical delivery module 203) and are adapted to deliver and position a cleaning gas into the metrology assemblies 291, 292 to remove any deposited material from components in the metrology assemblies 291, 292 during a cleaning process. In one embodiment, the cleaning gas may include gases such as fluorine (F₂) gas, chlorine (Cl₂) gas, bromine (Br₂) gas, or iodine (I₂) gas. In another embodiment, the cleaning gas may include a gas comprising hydrogen iodide (HI), hydrogen chloride (HCl), hydrogen bromide (HBr), hydrogen fluoride (HF), nitrogen trifluoride (NF₃), and/or other similar gases. In one embodiment, diatomic chlorine (Cl₂) gas is used as the cleaning gas. In another embodiment, diatomic fluorine (F₂) gas is used as the cleaning gas. In one embodiment, the showerhead 204 has a plurality of first metrology ports 296 and/or a plurality of second metrology ports 297, and the showerhead assembly 201 has a respective plurality of first and/or second metrology assemblies 291, 292 and first and/or second purge gas assemblies 291A, 292A attached thereto, respectively.

FIG. 3 is a schematic, cross-sectional view of the first metrology assembly 291 attached to the showerhead 204 at the first metrology port 296 according to one embodiment of the present invention. In one embodiment, the first metrology assembly 291 includes a pyrometer assembly 320 attached to an optical element 301 that extends into the tube 298 of the first metrology port 296. The optical element 301 may be a sapphire rod, a sapphire rod coated with reflecting material, or a fiber optic cable with a core and integrated cladding. The optical element 301 and pyrometer assembly 320 are used to gather valuable processing temperature data during deposition processes in the chamber 102. The temperature data may be analyzed and stored for diagnostic purposes and/or used in feedback temperature control during processing. However, during processing, precursor gases may migrate from the processing volume 208 into the first metrology port 296 and into contact with the transmission surface 301A of the optical element 301 and components of the pyrometer assembly 320 and deposit material thereon. The transmission surface 301A is generally a surface through which the IR radiation transmitted from a body (e.g., substrate), which is disposed in the processing volume 208 of the processing chamber 102, is received before the IR radiation is transmitted through the optical element 301 to an optical sensor disposed in the pyrometer assembly 320. As a result of the undesirable deposition, the temperature data gathered by the pyrometer assembly 320 is unreliable, which results in unreliable diagnostic and control data. Thus, it is desirable to prevent and/or remove such unwanted deposition.

In one embodiment, in order to prevent and/or remove unwanted deposition of material on the optical element 301 and components of the pyrometer assembly 320, the first purge gas assembly 291A is positioned between the first metrology assembly 291 and the showerhead 204. The purge gas assembly 291A may be attached to both the showerhead 204 and the pyrometer assembly 320 via suitable fasteners (not shown). The purge gas assembly 291A may include a sheath 305 positioned concentrically about the optical element 301. In one embodiment, the sheath 305 is a tube made of a refractory and/or optically absorbing material, such as silicon carbide, silicon carbide coated graphite, silicon nitride, or aluminum nitride. In one embodiment, the sheath 305 is attached to a coupler 315 and extends into the tube 298 of the first metrology port 296.

In one embodiment, the coupler 315 includes a first inlet 316 that fluidly couples the purge gas source 282 with an aperture 317 disposed through a wall of the sheath 305. In one embodiment, the first inlet 316 is also coupled to a cleaning gas source. Thus, the purge gas (during deposition operations) or the cleaning gas (during cleaning operations) flows through the first inlet 316, the aperture 317, and into an interior region 315A of the sheath 305 surrounding the optical element 301. The gas then flows through the interior region 315A of the sheath 305, about the optical element 301, and through the showerhead 204 into the processing volume 208 of the chamber 102. During deposition operations, the concentric flow of purge gas across the optical element 301 prevents the precursor gases located in the processing volume 208 from migrating into the sheath 305 and depositing material on the transmission surface 301A of the optical element 301. During cleaning operations, the concentric flow of cleaning gas across the optical element 301 acts to remove deposited material from the transmission surface 301A of the optical element as well as the interior surface of the sheath 305.

In one embodiment, the coupler 315 includes a second inlet 318 that fluidly couples the purge gas source 282 with an outer interior region 298A of the tube 298 of the first metrology port 296 surrounding the sheath 305. In one embodiment, the second inlet 318 is also coupled to a cleaning gas source. Thus, the purge gas (during deposition operations) or the cleaning gas (during cleaning operations) flows through the second inlet 318 and through the outer interior region 298A of the tube 298 into the processing volume 208 of the chamber 102. During deposition operations, the additional concentric flow of purge gas about the sheath 305 and across the transmission surface 301A of the optical element 301 further prevents undesirable deposition of material on the transmission surface 301A of the optical element 301, resulting in the gathering of more reliable temperature information by the pyrometer assembly 320, by adding an additional “curtain” of gas that isolates the transmission surface 301A of the optical element 301. The additional gas flow is believed to help surround and support the gas flow delivered through the interior of the sheath 305 to promote the isolation of the transmission surface 301A of the optical element 301. During cleaning operations, the flow of cleaning gas acts to remove any deposited particles formed on the surfaces of the tube 298, the sheath 05, and the transmission surface 301A of the optical element 301.

FIG. 4A is a schematic, cross-sectional view of the second metrology assembly 292 attached to the second metrology port 297 of the showerhead 204 according to one embodiment of the present invention. In one embodiment, the second metrology assembly 292 includes an optical sensor assembly 420, such as an optical stress or deflection measurement device, attached to a coupler 412, and a sensor window 410 above the second metrology port 297. The optical sensor assembly 420 may be used to gather valuable metrology data during the processing of the substrates 240 in the chamber 102. However, during processing, processing gases from the processing volume 208 tend to migrate into the tube 298 of the second metrology port 297 adjacent the sensor window 410, which results in undesirable deposition of material on the sensor window 410. Such undesirable deposition prevents reliable metrology data gathering.

In one embodiment, to prevent and/or remove the undesirable deposition of material on the sensor window 410, the coupler 412 couples the optical sensor assembly 420 to the sensor window 410 via the second purge gas assembly 292A. The second purge gas assembly 292A may include a gas coupling 405 attached to the second metrology port 297 of the showerhead 204 and the coupler 412 via suitable fasteners (not shown). In one embodiment, the second purge gas assembly 292A further includes a gas distribution device 415 having a central aperture formed therethrough and positioned between the sensor window 410 and the second metrology port 297 of the showerhead 204 via the gas coupling 405. The gas coupling 405 may include a gas inlet 418 coupling the purge gas source 282 to the gas distribution device 415. In one embodiment, the gas inlet 418 is further coupled to a cleaning gas source.

FIG. 4B is a top view of the gas distribution device 415 depicted in FIG. 4A. In one embodiment, the gas distribution device 415 includes a flow control orifice 416, which fluidly couples an annular gas channel 417 in the gas distribution device 415 with the gas inlet 418. The annular gas channel 417 is fluidly coupled with its central aperture and the interior of the tube 298 of the second metrology port 297 through a plurality of distribution channels 419 formed in a center ridge 419A of the gas distribution device 415. In one embodiment, the plurality of distribution channels 419 are positioned at an angle relative to the center of the sensor window 410 to create a vortex of gas flowing through the gas distribution device 415 near a lower surface 411 of the sensor window 410. Thus, a purge gas (during deposition operations) or a cleaning gas (during cleaning operations) flows, through the inlet 418 in the gas coupling 405, through the flow control orifice 416, and into the annular gas channel 417 in the gas distribution device 415. The gas then flows from the annular gas channel 417, through the plurality of distribution channels 419 toward the lower surface 411 of the sensor window 410. As previously described, the plurality of distribution channels 419 are angled such that the gas flowing therethrough creates a vortex near the lower surface 411 of the sensor window 410. In the case of a purge gas flowing during deposition operations, the gas vortex prevents processing gases from the processing volume 208 of the chamber 102 from depositing material on the lower surface 411 of the sensor window 410. In the case of a cleaning gas flowing during cleaning operations, the gas vortex acts to remove any deposited material from the lower surface 411 of the sensor window 410. In either case, the vortex of gas is then pushed through the tube 298 of the second metrology port 297 and into the processing volume 208 by the incoming gas delivered through the distribution channels 419. As a result, the purge gas assembly 292A directs a purge gas to prevent undesirable deposition on the sensor window 410 of the second metrology assembly 292, resulting in more reliable metrology data gathering during deposition processes. Further, during cleaning operations, the purge gas assembly 292A directs a cleaning gas to remove any deposited material from the sensor window 410 of the second metrology assembly 292, resulting in more reliable metrology data gathering during deposition processes.

FIG. 5A is a schematic, cross-sectional view of the second metrology assembly 292 attached to the second metrology port 297 of the showerhead 204 according to another embodiment of the present invention. In one embodiment, the second metrology assembly 292 includes an optical sensor assembly 520, such as an optical stress or deflection measurement device, attached to a coupler 512, and a sensor window 510. The optical sensor assembly 520 may be used to gather valuable metrology data during the processing of the substrates 240 in the chamber 102. As previously described, during processing, processing gases from the processing volume 208 tend to migrate into the tube 298 of the second metrology port 297 into a region surrounding the sensor window 510, which results in undesirable deposition of material on the sensor window 510. Such undesirable deposition prevents reliable metrology data gathering.

In one embodiment, to prevent and/or remove undesirable deposition of material on the sensor window 510, the coupler 512 couples the optical sensor assembly 520 to the sensor window 510 via the second purge gas assembly 292A. The second purge gas assembly 292A may include a gas coupling 505 attached to the showerhead 204 and the coupler 512 via suitable fasteners (not shown). The gas coupling 505 may include a gas inlet 518 disposed through the gas coupling 505, which couples the purge gas source 282 to a central region near a lower surface 511 of the sensor window 510 and into the interior of the tube 298 of the second metrology port 297. In one embodiment, the gas inlet 518 is further coupled to a cleaning gas source. In one embodiment, the purge gas (during deposition processes) or the cleaning gas (during cleaning processes) flows through the gas inlet 518, onto the lower surface 511 of the sensor window 510, through the tube 298, and into the processing volume 208 of the chamber 102. The resulting flow of purge gas helps prevent processing gases from the processing volume 208 of the chamber 102 from depositing material on the surface of the sensor window 510 during deposition processes. During cleaning operations, the flow of cleaning gas acts to remove any deposited material from the surface of the sensor window 510.

In one embodiment, in order to increase the effectiveness of the purge gas assembly 292A described with respect to FIG. 5A, the sensor window 510 may be configured such that the gas flowing through the gas inlet 518 contacts the surface of the sensor window 510 at a desirable angle. FIG. 5B is a schematic, cross-sectional view of the sensor window 510 as it is positioned in the second metrology assembly 292 in FIG. 5A according to one embodiment. In the embodiment, depicted in FIG. 5B, the sensor window 510 is in the shape of a wedge, such that the lower surface 511 of the sensor window 510 is situated at an angle A with respect to the gas inlet 518, and the upper surface 513 of the sensor window 510 is situated at an angle B with respect to the gas inlet 518. In one embodiment, the angles A and B are between about 1° and about 3°. In one embodiment, the angles A and B are about 2°. FIG. 5C is a schematic, cross-sectional view of the sensor window 510 as it is positioned in the second metrology assembly 292 in FIG. 5A according to another embodiment. In the embodiment, depicted in FIG. 5C, the sensor window 510 has substantially parallel upper and lower surfaces 513, 511, but the sensor window 510 is positioned in the second metrology assembly 292 such that the lower surface 511 is at an angle C with respect to the gas inlet 518. In one embodiment, the angle C is between about 1° and about 4°. In one embodiment, the angle C is about 2.5°.

In the embodiments of FIGS. 5B and 5C, the sensor window 510 is positioned such that the lower surface 511 is at a desired angle with respect to the gas inlet 518. In such a configuration, the gas flowing through the gas inlet 518 in the gas coupler 505 contacts the lower surface 511 of the sensor window 510 at a desirable angle to create a desirable distribution and flow of gas across the lower surface 511 of the sensor window 510. The gas then flows through the tube 298 of the second metrology port 297 and into the processing volume 208 of the chamber 102. As a result, during deposition processes, the purge gas assembly 292A prevents undesirable deposition on the sensor window 510 of the second metrology assembly 292, resulting in more reliable metrology data gathering during deposition processes. Further, during cleaning operations, the purge gas assembly 292A directs a cleaning gas to remove any deposited material from the sensor window 510 of the second metrology assembly 292, resulting in more reliable metrology data gathering during deposition processes.

FIG. 6A is a bottom view of the showerhead assembly 201 shown in FIG. 2 according to one embodiment of the invention. In one embodiment, the showerhead assembly 201 includes a plurality of first metrology ports 296 arranged in a radial line from the center of the showerhead 204 to the perimeter of the showerhead 204. In such an embodiment, the first metrology ports 296 are arranged so that the first metrology assemblies 291 can detect the temperature distribution from the center to the perimeter of the processing volume 208 of the processing chamber 102. In one embodiment, the substrates 240 are arranged in a circular pattern about the center point of the carrier plate 112 (FIG. 2), and the carrier plate 112 is rotated during processing. In such an embodiment, the showerhead assembly 201 may include a plurality of second metrology ports 297 positioned concentrically about the center of the showerhead 204 at a position such that they are centered over a central portion of the substrates 240 disposed on the carrier plate 112 as it is rotated during processing.

FIG. 6B is a bottom view of the showerhead assembly 201 shown in FIG. 2 according to another embodiment of the invention. In one embodiment, the showerhead assembly 201 includes one first metrology port 296 positioned at the center of the showerhead 204 and a plurality of first metrology ports 296 arranged in a concentric pattern about the center of the showerhead 204. As described with respect to FIG. 6A, the showerhead assembly 201 may further include a plurality of second metrology ports 297 positioned concentrically about the center of the showerhead 204 at a position such that they are centered over a central portion of the substrates 240 disposed on the carrier plate 112 as it is rotated during processing.

FIG. 6C is an enlarged schematic view of a portion of the bottom surface of the showerhead 204. In one embodiment, the inner and outer gas conduits 246, 245 are positioned across the surface of the showerhead 204 in a hexagonal close-packed arrangement as shown.

Referring back to FIG. 2, a lower dome 219 may be disposed at one end of a lower volume 210, and the substrate carrier plate 112 may be disposed at the other end of the lower volume 210. The substrate carrier plate 112 is shown in an elevated, process position, but may be moved to a lower position where, for example, the substrates 240 may be loaded or unloaded. An exhaust ring 220 may be disposed around the periphery of the substrate carrier plate 112 to help prevent deposition from occurring in the lower volume 210 and also help direct exhaust gases from the chamber 102 to exhaust ports 209. The lower dome 219 may be made of transparent material, such as high-purity quartz, to allow light to pass through for radiant heating of the substrates 240. The radiant heating may be provided by a plurality of inner lamps 221A and outer lamps 221B disposed below the lower dome 219. Reflectors 266 may be used to help control exposure of the chamber 102 to the radiant energy provided by the inner and outer lamps 221A, 221B. Additional rings of lamps (not shown) may also be used for finer temperature control of the substrates 240.

The chemical delivery module 203 supplies chemicals to the MOCVD chamber 102. Reactive gases (e.g., first and second precursor gases), carrier gases, purge gases, and cleaning gases may be supplied from the chemical delivery system through supply lines and into the chamber 102. In one embodiment, the gases are supplied through supply lines and into a gas mixing box where they are mixed together and delivered to the showerhead assembly 201. Generally supply lines for each of the gases include shut-off valves that can be used to automatically or manually shut-off the flow of the gas into its associated line, and mass flow controllers or other types of controllers that measure the flow of gas or liquid through the supply lines. Supply lines for each of the gases may also include concentration monitors for monitoring precursor concentrations and providing real time feedback. Backpressure regulators may be included to control precursor gas concentrations. Valve switching control may be used for quick and accurate valve switching capability. Moisture sensors in the gas lines measure water levels and can provide feedback to the system software which in turn can provide warnings/alerts to operators. The gas lines may also be heated to prevent precursors and cleaning gases from condensing in the supply lines. Depending upon the process used some of the sources may be liquid rather than gas. When liquid sources are used, the chemical delivery module includes a liquid injection system or other appropriate mechanism (e.g., a bubbler) to vaporize the liquid. Vapor from the liquids is then usually mixed with a carrier gas as would be understood by a person of skill in the art.

The remote plasma system 226 can produce a plasma for selected applications, such as chamber cleaning or etching residue from a process substrate. Plasma species produced in the remote plasma system 226 from precursors supplied via an input line are sent via a conduit 204D for dispersion through the showerhead 204 to the MOCVD chamber 102. Precursor gases for a cleaning application may include chlorine containing gases, fluorine containing gases, iodine containing gases, bromine containing gases, nitrogen containing gases, and/or other reactive elements. The remote plasma system 226 may also be adapted to deposit CVD layers flowing appropriate deposition precursor gases into remote plasma system 226 during a layer deposition process. In one embodiment, the remote plasma system 226 is used to deliver active chlorine species to the processing volume 208 for cleaning the interior of the MOCVD chamber 102.

The temperature of the walls of the MOCVD chamber 102 and surrounding structures, such as the exhaust passageway, may be further controlled by circulating a heat-exchange liquid through channels (not shown) in the walls of the chamber 102. The heat-exchange liquid can be used to heat or cool the chamber body 202 depending on the desired effect. For example, hot liquid may help maintain an even thermal gradient during a thermal deposition process, whereas a cool liquid may be used to remove heat from the system during an in-situ plasma process, or to limit formation of deposition products on the walls of the chamber. This heating, referred to as heating by the “heat exchanger”, beneficially reduces or eliminates condensation of undesirable reactant products and improves the elimination of volatile products of the process gases and other contaminants that might contaminate the process if they were to condense on the walls of cool vacuum passages and migrate back into the processing chamber during periods of no gas flow.

In one embodiment, during processing, a first precursor gas flows from the first processing gas channel 204A in the showerhead 204 and a second precursor gas flows from the second processing gas channel 204B formed in the showerhead 204 towards the surface of the substrates 240. As noted above, the first precursor gas and/or second precursor gas may comprise one or more precursor gases or process gasses as well as carrier gases and dopant gases which may be mixed with the precursor gases. The draw of the exhaust ports 209 may affect gas flow so that the process gases flow substantially tangential to the substrates 240 and may be uniformly distributed radially across the substrate deposition surfaces in a laminar flow. In one embodiment, the processing volume 208 may be maintained at a pressure of about 760 Torr down to about 80 Torr.

Exemplary showerheads that may be adapted to practice embodiments described herein are described in U.S. patent application Ser. No. 11/873,132, filed Oct. 16, 2007, now published as US 2009-0098276, entitled MULTI-GAS STRAIGHT CHANNEL SHOWERHEAD, U.S. patent application Ser. No. 11/873,141, filed Oct. 16, 2007, now published as US 2009-0095222, entitled MULTI-GAS SPIRAL CHANNEL SHOWERHEAD, and U.S. patent application Ser. No. 11/873,170, filed Oct. 16, 2007, now published as US 2009-0095221, entitled MULTI-GAS CONCENTRIC INJECTION SHOWERHEAD, all of which are incorporated by reference in their entireties. Other aspects of the MOCVD chamber 102 are described in U.S. patent application Ser. No. 12/023,520, filed Jan. 31, 2008, published as US 2009-0194024, and titled CVD APPARATUS, which is herein incorporated by reference in its entirety.

In summary, embodiments of the present invention include a showerhead assembly having separate inlets and channels for delivering separate processing gases into a processing volume of the chamber without mixing the gases prior to entering the processing volume. In one embodiment, the showerhead includes metrology ports with purge gas assemblies configured and positioned to deliver a purge gas to prevent deposition thereon, thus increasing the reliability of data gathered by metrology assemblies attached to the metrology ports. In one embodiment, the metrology port is configured to receive a temperature measurement device, and the purge gas assembly is a concentric tube configuration configured to prevent deposition on components of the temperature measurement device, resulting in more reliable temperature data gathered thereby. In another embodiment, the metrology port has a sensor window and is configured to receive an optical measurement device. The purge gas assembly and sensor window are configured to prevent deposition on the sensor window, resulting in more reliable data gathered by the optical measurement device.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. For example, certain embodiments of the showerhead assembly 201 do not include all of the channels 204A-C. In addition, certain embodiments of the showerhead assembly 201 do not include any of the channels 204A-C. 

1. A showerhead assembly, comprising: a showerhead having: a first metrology port defining an interior region and extending through the showerhead; and a second metrology port extending through the showerhead; a first metrology assembly having an optical element that is at least partially disposed within the interior region of the first metrology port; a first purge gas assembly having a first gas inlet coupled to a purge gas source and configured to direct a purge gas through the interior region of the first metrology port to prevent deposition of material on the optical element; a second metrology assembly having a sensor window disposed adjacent the second metrology port; and a second purge gas assembly having a gas inlet coupled to the purge gas source and configured to direct the purge gas toward the sensor window to prevent deposition of material thereon.
 2. The assembly of claim 1, wherein a sheath is concentrically disposed about the optical element and within the interior region.
 3. The assembly of claim 2, wherein the sheath has an aperture in fluid communication with the first gas inlet.
 4. The assembly of claim 3, wherein the first purge gas assembly has a second gas inlet fluidly coupled to the purge gas source and configured to direct the purge gas through the interior region of the first metrology port, wherein the first gas inlet is in fluid communication with a first portion of the interior region between the optical element and a first surface of the sheath, and wherein the second gas inlet is in fluid communication sheath.
 5. The assembly of claim 1, wherein the second purge gas assembly further comprises a gas distribution device having an annular channel in fluid communication with the gas inlet.
 6. The assembly of claim 5, wherein the gas distribution device is configured to direct the purge gas into a vortex adjacent the sensor window.
 7. The assembly of claim 6, wherein the gas distribution device has a plurality of passages fluidly connecting the annular channel with a central aperture formed through the gas distribution device.
 8. The assembly of claim 1, wherein the showerhead has: a first gas channel formed in the showerhead; and a second gas channel formed in the showerhead and isolated from the first gas channel, wherein the first and second metrology ports extend through the first gas channel and the second gas channel.
 9. The assembly of claim 8, wherein the showerhead has a temperature control channel formed in the showerhead and isolated from the first and second gas channels, wherein the first and second metrology ports extend through the temperature control channel.
 10. The assembly of claim 1, wherein the first and second purge gas assemblies are each coupled to a cleaning gas source.
 11. The assembly of claim 1, wherein the sensor window has a cross-section in the shape of a wedge.
 12. The assembly of claim 1, wherein the sensor window is positioned at an angle between about 1 degree and about 4 degrees with respect to the gas inlet of the second purge gas assembly.
 13. A showerhead assembly, comprising: a showerhead having a metrology port defining an interior region and extending through the showerhead; a metrology assembly having an optical element that is at least partially disposed within the interior region of the metrology port; and a purge gas assembly having a first gas inlet coupled to a purge gas source and configured to direct a purge gas toward the optical element to prevent deposition of material thereon, wherein a sheath is concentrically disposed about the optical element and within the interior region, and wherein the sheath has an aperture in fluid communication with the first gas inlet.
 14. The assembly of claim 13, wherein the purge gas assembly has a second gas inlet fluidly coupled to the purge gas source and configured to direct the purge gas through the first metrology port.
 15. The assembly of claim 13, wherein the showerhead has: a first gas channel formed in the showerhead; and a second gas channel formed in the showerhead and isolated from the first gas channel, wherein the metrology port extends through the first gas channel and the second gas channel.
 16. The assembly of claim 15, wherein the showerhead has a temperature control channel formed through the showerhead and isolated from the first and second gas channels, wherein the metrology port extends through the temperature control channel.
 17. A showerhead assembly, comprising: a showerhead having a metrology port extending through the showerhead; a metrology assembly having a sensor window disposed adjacent the metrology port; and a purge gas assembly having a gas inlet coupled to a purge gas source and a gas distribution device having an annular channel in fluid communication with the gas inlet, wherein the gas distribution device is configured to direct the purge gas into a vortex adjacent the sensor window.
 18. The assembly of claim 17, wherein the gas distribution device has a plurality of passages fluidly connecting the annular channel with a central aperture formed through the gas distribution device.
 19. The assembly of claim 17, wherein the showerhead has: a first gas channel formed in the showerhead; and a second gas channel formed in the showerhead and isolated from the first gas channel, wherein the metrology port extends through the first and second gas channels.
 20. The assembly of claim 19 wherein the showerhead has a temperature control channel formed in the showerhead and isolated from the first and second gas channels, wherein the metrology port extends through the first and second gas channels. 